Ionic contact is established and maintained between electrodes and soil in ohmic heating of a subsurface formation for recovery of volatile... Show moreIonic contact is established and maintained between electrodes and soil in ohmic heating of a subsurface formation for recovery of volatile and semi-volatile materials, such as hazardous waste, hydrocarbon-like materials, and valuable minerals having thermally responsive properties. A compressed, dry sponge is wrapped around an electrode, which is then inserted into a bore hole. A conductive liquid is added to the bore hole, causing the sponge to swell, creating a stable and substantial interface for the flow of heating currents. Sponsorship: IIT Research Institute United States Patent Show less